This invention relates to twin spool gas turbine engines and particularly to means for disassembling the high turbine rotor without a major disassembly of the engine.
Two conflicting design features of a high speed twin spool gas turbine engine have contributed to the problem of the removal of the high turbine rotor without requiring a major disassembly of the engine. The first of these features is the fact that in order to obtain the required critical speed of the low shaft it was necessary to increase its diameter in the region of the high compressor section. This "bottled" low shaft, then could not be removed from either end of the engine without high compressor disassembly inasmuch as the diameter of the low shaft is larger than the inner diameter of certain major engine components. Additionally, the high speed shafting features an internal coupling which joins the compressor and turbine rotor with overlapping hubs. The overlap serves to preclude turbine overspeed resulting from shaft torsional failure resulting from an overheated bearing.
We have found that we can remove the high turbine rotor without a major disassembly while incorporating the design features enumerated in the above. In accordance with this invention we provide a thin-wall tool adapted to fit between the small annular space between the high and low shafts which engages an internal spline provided on the high coupling nut. To obviate the problem occasioned by the low torsional buckling strength of the tool, we provide an additional set of spline teeth on the tool that engage external spline teeth provided on the low shaft. Hence, this tool serves to torsionally connect both shafts permitting the operator to rotate the low speed shaft so as to unscrew the high coupling nut to disconnect the high turbine without removing the low shaft.